When it comes to the grisly world of organised terrorism, it is probably a vain task to distinguish between degrees of evil. And yet dissident republicanism - whether in the form of the so-called Real IRA or Continuity IRA, two separate organisations now said to be collaborating - seems bent on plumbing new depths.

Not content with staging the deadliest atrocity in 30 years of the troubles, killing 29 civilians in the bombing of Omagh town centre in August 1998, the rejectionists of republicanism have now declared war on the truth itself.

They will doubtless claim that BBC Television Centre is a citadel of the British state and therefore a "legitimate target". But more plausible is the notion that the hardmen were angered by Panorama's recent expose of the Omagh bombers and that Sunday's planned "spectacular" was payback. This says much about the fascistic impulses of the Real IRA and its ilk: they regard journalists courageous enough to tell the truth as targets for murder and maiming. Dissident republicanism's American backers should take note. Before they next dip in their pocket to make a sentimental donation for the boys' struggle back home, they should remember their own hallowed First Amendment guaranteeing freedom of speech - and recall the terrorists' contempt for it.

Confronted with such malice, it is no wonder that people revert to their default positions - with the perennial Unionist demand for decommissioning the most instant reaction. Witness David Trimble's declaration that dissidents were using "material and expertise" leaked from the mainstream IRA and so extra pressure had to be brought to bear on the latter to hand over its guns.

And yet this logic, while superficially appealing, is not sound. First, it ignores what was always the most stubborn fact about disarmament, best stated by the nationalist leader John Hume: "You can hand over a gun on Monday, only to buy another one on Tuesday." In other words, even if the Provisional IRA handed in every last one of its weapons, it would not prevent the likes of the Real IRA from striking again. They can get hold of explosives easily - whether of the homemade, fertiliser-based variety or byimporting them: latest reports suggest the Balkans has become a source. Moreover, if the Real IRA have got hold of some Provisional arms, then clearly the latter cannot hand them over, even if they wanted to. As always, the key point about weapons is the intent to use them. The Real IRA have that intent, and no amount of Provo decommissioning will prevent them acting on it.

In fact, the reverse is true. It is the issue of disarmament which, more than any other, acts as a recruiting sergeant for dissident republicanism. When Gerry Adams or Martin McGuinness is seen even to be negotiating the issue, hardliners are able to brand the Sinn Fein leaders as sellouts on the brink of symbolic surrender.

By continuing to push the question, Unionists inadvertently confirm the hardliners' core argument: that the peace process is just a ruse to disarm republicans. When there have already been more than 50 pipebomb attacks on Catholic homes this year, hardliners strike a chord when they ask why republicans alone are pressed so hard to give up their weapons.

Unionists should follow the wise counsel of the Northern Ireland secretary, John Reid. The best way to marginalise the dissidents is to prove that "politics works". When Sinn Fein can boast of progress, there will be no constituency to nourish the Real IRA or its murderous collaborators.